Britain's defence chiefs were said to have been deeply unamused when a Russian nuclear submarine slipped away from the gaze of our military spies.

I wrote this morning about how the "layer cake" of surveillance lost the submarine last summer as it left the headquarters of the old Soviet northern fleet in Severomorsk near Murmansk. It was picked up three weeks later on patrol in the Atlantic.

Does this matter? Rob Hewson, editor of Jane's Air-Launched Weapons, thinks not. This is what he told me:

The fact that we cannot track a Russian missile submarine, of which there are very few not doing very much...Is that the big deal that it used to be?

Liam Fox, the defence secretary, would disagree. He obviously thinks it is important to monitor the Russians with Britain's "spy in the sky". This is the Nimrod MR2 plane, operating from RAF Kinloss, that was due to be replaced by the Nimrod MRA4.

In his famous letter to the prime minister, leaked to the Daily Telegraph, Fox warned that scrapping the Nimrod MRA4 could jeopardise Britain's Trident nuclear deterrent:

Deletion of the Nimrod MR4 will limit our ability to deploy maritime forces rapidly into high-threat areas, increase the risk to the Deterrent, compromise maritime CT (counter terrorism), remove long range search and rescue, and delete one element of our Falklands reinforcement plan.

Fox has lost that particular battle because the Nimrod MRA4 has been scrapped in the strategic defence and security review. MPs, who share Fox's concerns about Russia, would no doubt like to ask whether it is wise to scrap the next generation of the Nimrod "spy in the sky".

But MPs will struggle to put any questions to Fox this week. The national security strategy is to be launched today by William Hague. David Cameron will launch the defence review in the Commons tomorrow.

Fox is learning what happens when you cross David Cameron and George Osborne. Just ask victims of the mafia in Sicily.